The basic snorkel, which facilitates breathing atmospheric air while the face is submersed in a body of water, has been present for centuries of time. In a common and simple form, the snorkel includes a breathing conduit. The breathing conduit typically has a mouthpiece connected to one end of the conduit. The other end of the conduit is positioned in the air above the water and the user's head to allow inhalation of air while the user's face or mouth is underwater.
The basic snorkel has been improved, enhanced and built upon over the years. Many designs, structures and modifications to snorkels have been created to improve or enhance the experience of the user while swimming and/or diving. Some of the more relevant patents and published patent applications include:
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As is evident from the above patents, numerous problems have been addressed by various snorkel designs. However, to the best of this inventor's knowledge, no attention has been given to the physiologic impact of the compressive forces of ambient water on the respiration, specifically in exhalation, of the user of a surface-breathing, or near-surface breathing, snorkel.
Scuba regulators, scuba equipment, snuba tubes and other snuba equipment are well known to persons of ordinary skill in the art. Embodiments of my invention can be adapted for use with the foregoing as well as new innovations in these areas.
Several devices in the related field of “snuba” have confirmed that pressure-assistance is necessary to facilitate inhalation at the modest depths achieved with snuba. But once again, to the best of this inventor's knowledge, no attention has been given to the expiratory flow rate at such depths. Even scuba regulators, which facilitate inhalation at much greater depths, have not, to the best of this inventor's knowledge, specifically addressed the greatly increased expiratory flow rates that naturally occur at these even greater depths.
In the case of the snorkel the user is typically in either a state of immersion (meaning that the body is within the water, while the airways communicate at atmospheric pressure) or in a state of submersion (meaning that both the body and the airways are exposed to ambient water pressure). From a practical standpoint for a snorkel user, most respiration necessarily occurs while surface swimming in the state of immersion. In this state, the conventional snorkel exchanges air at atmospheric pressure with the lungs, which lungs are acted upon by the greater compressive pressures of ambient water. Hence, compared to being completely out of the water, a greater effort is required to expand the lungs in inspiration and a lesser effort is required for exhalation, i.e., the expiratory flow rate is faster than the inhalation flow rate. Inasmuch as inhalation occupies only a small temporal component of the complete respiratory cycle, this faster exhalation component also results in a substantially shorter respiratory cycle and more inhalations per minute. In addition, as the user is exposed to the compressive effects of the ambient water pressure, during inhalation, a greater work of breathing is incurred and, over time, his or her inspiratory muscles progressively fatigue, resulting in smaller functional lung capacity, a relatively greater adverse contribution of the snorkel and bronchial dead spaces with each breath, and the possibility of atelectasis (collapse of the alveolar/gas exchange sacs).
Embodiments of the snorkel presented herein can serve to substantially reduce the overall work of breathing by balancing the expiratory forces, slowing the respiratory cycle, reducing the repetitive work of inhalation against compressive ambient water pressures, and/or minimizing the risk of developing atelectasis.
Furthermore, several other benefits may be realized by embodiments of my invention. By increasing the pressure within the snorkel's main (inhalation) tube, the inhalation valve at the top end of tube can be maintained in a closed position, except during active inhalation, thereby significantly reducing the internal exposure to splash water, and even reducing the internal exposure to flood water upon submersion; however, the inhalation valve does not absolutely close while submersed, beneficially allowing the user to voluntarily draw on a small amount of residual air. The pressure amounts to positive end-expiratory pressure (“PEEP”) which may result in physiologic benefit to some users, particularly those with obstructive lung diseases, such as asthma and emphysema.
Many aspects of human physiology become involved here, but in a simplistic overview, PEEP slows respiratory rate and tends to increase functional lung volumes, but also tends to slow venous blood return to the heart. In the water, however, venous blood return to the heart is already greatly improved simply by the compressive forces of ambient water. A slowed respiratory rate is preferred as each inhalation must displace water, significantly increasing the work of breathing, inspiratory muscle fatigue, and the associated anxiety that accompanies many skin divers. Furthermore, the increase in lung volume, time-averaged over the complete respiratory cycle, enhances the buoyancy of the user.